I stumbled upon this when trying to understand what one misses when using Henkin instead of standard semantics for higher order logic.

I simply learn maths by lazy evaluation. (T. Altenkirch, FLoC 2018)

His answer when I asked whether one needs to be a blessed mathematician in order to understand HoTT.

A good definition is worth a hundred theorems. (unknown)

No more "proofs" that look more like LSD trips than coherent chains of logical arguments. (T. Nipkow, G. Klein, preface in Concrete Semantics)

Great book for a great course that I took at TU Munich - the thing that got me into interactive theorem proving.

For any (even infinite) collection of pairs of shoes, one can pick out the left shoe from each pair to obtain an appropriate selection; this makes it possible to directly define a choice function, but for an infinite collection of pairs of socks (assumed to have no distinguishing features), such a selection can be obtained only by invoking the axiom of choice. (B. Russell, see https://en.wikipedia.org/wiki/Axiom_of_choice)